According to municipalities, government agencies, environmentalists and the public in general, odour and potential pollution sources emanating from swine facilities are the main issues that the hog industry needs to address in order to sustain its development. The most intense source of odour from livestock facilities occurs during manure handling and land application. The manure from hogs can generally be classified as low volume, high strength liquid waste. That is, waste of high strength requires high levels of oxygen to biodegrade and may contaminate ground water. Typically, most commercial hog operations feature under-floor manure storage pits. These pits are situated beneath the barns and store the manure until the manure is emptied from the pit and transferred to mid-term storage lagoons. The odour problem that arises when the manure is stored in such a manner is a result of the anaerobic conditions that exist in the lagoon. Typically, aerobic conditions exist only in the layer of manure that is in contact with air and the malodorous gases produced anaerobically beneath this layer gradually diffuse to the surface, which in turn raises the prospect of public annoyance and creates health concerns for the swine herd and the barn workers. Conditions where anaerobic processes under very low dissolved oxygen (&lt;0.5 mg/l) conditions occur are referred to as anoxic conditions. Current methods used in controlling odour production during manure handling and land application have only been capable of suppressing or delaying odour production. Without an adequate treatment, producers are forced to handle manure that is highly non-homogeneous, which can cause a variety of technical and mechanical related problems. Therefore, a method of waste treatment must ensure odour reduction or elimination as well as a reduction in solids content or volume and waste strength. Waste strength is directly related to the Biological Oxygen Demand (BOD) of the waste. The BOD defines the waste strength in that it depicts the amount of oxygen required by the waste in order to biodegrade. Such a method will reduce handling concerns and pollution such as ground water contamination and/or air pollution caused by the malodorous gases. Furthermore, the treated waste produced should be a low strength waste and have high nutrient content (nitrogen, phosphorus, potassium) which is essential for fertilizer value.
It is of note that nutrient application to farm land must be balanced with the ability of the crops to utilize the nutrients applied. That is, excess nutrients in the fertilizer that are not absorbed by the soil are likely to contaminate the aquifers and surface water bodies. As a result, the amount of fertilizer that can be applied to a given plot of land is highly dependent upon the local soil conditions, hydrology, geology and geography. However, in many cases, it is not cost effective for swine producers to haul raw manure long distances if the land surrounding the facility is already nutrient rich. Clearly, in cases such as these, it would be preferable to be able to separate the nutrients from the manure, thereby producing a concentrated fertilizer. As a result, the condensed fertilizer could be cost effectively transported and applied to farm land significant distances away from the swine production facility.